BBC Second Processor Tube ULA (was Re: What kind of IC is this)

Philip Pemberton classiccmp at
Wed Dec 31 19:20:50 CST 2008

Jules Richardson wrote:
> Not *completely*, AFAIK - although there are fragments all over the 
> place. I think there's enough amassed wisdom around now that it *could* 
> be done though, because the software to drive either side is understood 
> enough, as is the electrical (physical) interface, and there are still 
> survivors of all the vintage hardware which made use of the ULA.

What's available appears to be fairly thin on the ground though. A quick 
search on 'the bay' revealed tons of Master 128s and BBC Bs, but nary a second 
processor in sight.

I'd feel a bit bad if I ended up killing a ULA or a 2nd processor though :-/

> The problem is that very few people have both a grasp on that knowledge 
> and the ability to do the necessary electronic design - it's only really 
> worth it for a drop-in replacement (i.e. a single chip or a very small 
> daughter-board to plug into the ULA's 40-pin to DIP socket) because (as 
> Phil says) it'd be a reasonably large board to do it as discrete logic.

Oh, is that a challenge I hear? :)

Once I've sorted the floppy disc R/W project out (probably around Easter), I'd 
be more than happy to have a crack at cloning the Tube ULA. Seems Sprow has a 
few ULAs left, and one of those (assuming it's working) should be enough to 
clone the thing, but a 6502 2proc (either cheesewedge or internal, as long as 
it works on a Master 128) might be handy for a bit of live testing, if such a 
thing proves necessary.

classiccmp at

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